Recently, with an increase in component density due to advances in electronic packaging techniques of integrated circuit (IC) elements, the density of heat generation in electronic equipment has greatly increased. As a result, the heat dissipation requirements within advanced electronic equipment have become increasingly more severe.
Air-cooled systems are commonly used to cool electronic equipment. Now, efforts to shrink electronic assemblies have placed multiple high heat flux parts within close proximity to each other, exceeding the capacity of present air-cooled technology.
Single-phase liquid cooled systems are also commonly used for cooling electronic components. Liquid cooling requires external condensing coils and/or significant plumbing requirements. Thus, liquid cooled systems are comparatively larger, heavier, and more costly.
Many prior known systems for cooling avionics equipment use heat pipes. The heat pipe is a sealed thermodynamic system relaying on internal evaporation and condensation cycles. It comprises an enclosure, a wicking material lining the internal walls of the enclosure, and a working fluid for saturating the wick. One end of the heat pipe is called the evaporator and serves to absorb heat energy. Vapor formed in an evaporator is transported to the other end of the heat pipe, called the condenser, and the heat energy is released. The liquid is returned to the evaporator through a wick structure on the inside of the heat pipe completing the process. The performance of this heat pipe is highly dependent on the operating temperature, wick dryout, and internal generation of non-condensable gases. Therefore, heat pipe technology has limited ability beyond cooling low-power electronic components.
Spray cooling can be used to cool high heat dissipation electronic components. Generally, spray cooling performs at greater heat extraction levels than other techniques. In a spray cooling system, liquid from a reservoir is pumped into the spray module. The fluid is sprayed onto the area to be cooled. The heat vaporizes the fluid, thereby absorbing or removing part of the heat. The excess liquid and vapor are drawn through a condenser using pumps. The pumps return the cooled fluid to the reservoir for recirculation. However, during the operation of the spray cooling system, non-condensable gases can be released from either the fluid or the materials of construction. These non-condensable gases degrade condenser performance by displacing the working vapors and by impeding the vapor contact with the condenser surface. Therefore, the generation of non-condensable gases undermines the heat extraction efficiency of both heat pipes and spray cooling modules.